Evolutionary delivery is a refinement of the practice of incremental delivery in which there is a vigorous attempt to capture feedback regarding the installed product, and use this to guide the next delivery. Naturally, the evolutionary goal is to best meet some difficult-to-predict need, such as the most frequently requested new features. Uniquely, the Evo method promotes when possible very short evolutionary delivery cycles of one or two weeks, so that each iteration delivers something useful to stakeholders.
To contrast "pure" incremental delivery with evolutionary delivery, in the former a plan is defined of several future deliveries feedback is not driving the delivery plan. In evolutionary delivery, there is no plan (or at least no fixed plan) of future deliveries; each is dynamically created based on emerging information. In practice, a marriage of some future prediction and feedback is obvious and common, and the two terms are used interchangeably.